Vibratory unit with seal



y 1967 F. G. HAMMITT ETAL 3,331,589

VIBRATORY UNIT WITH SEALING DEVICE Filed Feb. 8, 1965 m m m N m E ow. .0 WW W; m M w H moM wcRwll/ R D GHJY G M m-m 3i fMF 50 d P w United States Patent 3,331,589 VIBRATORY UNIT WITH SEAL Frederick G. Hammitt, 1306 Olivia St. 48104; Ramon Garcia, 400 Maynard, Apt. 701 48108; and Marion .1. Robinson, 1677 Broadway 48105, all of Ann Arbor, Mich; and Fazil Aydinmalnine, 2202 Massachusetts Ave., Washington, D.C. 20008 Filed Feb. 8, 1965, Ser. No. 431,106 5 Claims. (Cl. 259-116) ABSTRACT OF THE DISCLOSURE Vibratory horn apparatus having the horn provided with a shoulder and an annular sealing ring disposed between the shoulder and the container on which the horn member is mounted. Means is provided for urging the horn in a direction such that the horn shoulder compresses the sealing ring.

This invention relates generally to high-frequency vibratory units and more particularly to an improved sealing means and structure for units of this type.

Vibratory units of the type to which this invention relates include a vibratory horn and a driver for vibrating the horn such that one end of the horn, hereinafter called the working end, is vibrated at high frequency. The horn extends into a container having liquid in it which contacts the working end of the horn and which may be at an elevated temperature as high as the 1500-2000 F. range. The driver is usually a crystal oscillator, which utilizes the piezolectric elfect, or a magnetostrictive oscillator, which utilizes the phenomenon of magnetostriction. In any event the working end of the horn is usually vibrated at a very high frequency, for example, a frequency of 2-30 kc./sec., and the double amplitude of vibration is usually in the /23 mil range. This vibration of the horn in the liquid produces cavitation, so that vibratory units are usable commercially for cleaning, degassing and homogenizing of liquids. Such units are also usable for the production of cavitation for research purposes, for example, to determine the cavitation and cavitationerosion properties of various materials and materialfluid combinations. In a selected environment, various test specimens are mounted on the working end of the horn and positioned in contact with the test liquid. In vibratory units a seal may be necessary between the horn and the container at the point at which the horn enters the container since a gas may be introduced into the container as a cover gas for maintaining desired pressure or vacuum conditions in the container, and to otherwise provide the proper environment. However, the seal cannot restrict the amplitude or other characteristics of the vibration of the horn. Prior units have required flexible diaphragms or bellows which were of necessity permanently attached to the horn thereby detracting from the versatility of the horn. Furthermore these sealing devices were cumbersome and expensive to fabricate, and of short endurance.

It is an object of this invention to provide a containervibratory horn assembly, with an improved sealing structure for the vibratory horn, which is simple to assemble and disassemble, is economical to manufacture and use, provides an effective seal without restricting the vibration of the horn, and allows the maintenance of low temperature in the regions where seals are necessary, so that lowtemperature conventional sealing devices may be used.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims, and the accompanying drawing in which:

3,331,589 Patented July 18, 1867 illustrating the improved sealing means of this invention,

and showing the position of the nodes and antinodes in the standing wave forms induced in the transducer and horn assembly during operation of the particular unit shown in FIG. 1.

With reference to the drawing, means of this invention, indicated generally at 10, is illustrated in FIG. 1 incorporated in a high-frequency vibratory unit indicated generally at 12. The unit 12 consists generally of a high-frequency transducer and horn assembly 14 mounted on the top cover plate 16 of a container 18 filled with a liquid 19 to a level indicated at 20.

As shown in FIG. 1, the container 18 has a bottom wall 22 to which a filling tube 24 is connected for admitting fluid to and draining fluid from the container 18. At its upper end, the container 18 is formed with an outwardly flared conical top wall portion 25 which terminates in a radially outwardly extending flange 26 provided with a groove 28 in which a conventional sealing member, an O-ring 30 in the preferred embodiment of the invention, is positioned. A plurality of bolts 32 extends through the top plate 16 and into the flange 26 so as to compress the sealing member 30 and maintain the plate 16 in a fluidtight relation with the flange 26.

A passage 34 in the flange 26 and the cover plate 16 is connected to a gas inlet line 36 to enable an inert gas such as argon to be admitted into the top container 18, or to allow a connection to be made for evacuating the container 18. Argon, or other inert gas or vacuum, is admitted to the container 18 to flush undesirable gases therefrom when a reactable fluid 19 and/or material 102 is used, and in some cases argon or other gas may be used to maintain a desired pressure in the container 18 above the liquid level 20. An inner cone member 38 having an axial flanged opening 40 can be adjustably mounted, if desired, on the lower end portions of a plurality of support pins 42 (only one of which is shown) which are connected at their upper ends to the top plate 16. The purpose of the inner cone member 38 is to restrict circulation between the fluid near the surface and the main body of the fluid, and thus limit contamination of the fluid from the gas space. The inner cone is adjusted on the pins 42 to a desired position relative to the liquid level 20. In addition, a radiation shield 39 i provided between the surface of the material 19 and the cover plate 16 to reduce the amount of heat radiated from the material 19 to the plate 16. In the illustrated embodiment of the invention, a thermocouple 44 is mounted on the top plate 16 so that it extends downwardly through openings in the inner cone 38 and the radiation shield 39 into the fluid 19 for the purpose of measuring the temperature of the fluid 19. When the fluid is to be maintained at a predetermined temperature, the thermocouple 44 is utilized in conjunction with a suitable furnace or other heater (not shown) for maintaining the fluid 19 at the desired temperature, as well as providing an indication of liquid level by virtue of the ability of the thermocouple 44 to be moved in an axial direction.

The transducer and horn assembly elongated rod-shape horn member 50 which is illustrated as having separable upper and lower sections 52 and 54, respectively. A transducer driver, indicated generally at 56, is connected to the upper end of the horn member 50 and a counterweight 58 is attached to the upper end of the driver 56. In the illustrated form of the invention, the driver 56 consists of a pair of piezoelectric crystal 14 consists of an end of the' wafers 68 which are bonded to opposite sides of an aluminum spacer disk 62. An internal bolt 64, suitably insulated electrically, is secured to the counterweight 58, passes through the wafers 60 and the spacer 62, and is secured to the upper horn section 52. In a preferred embodiment of the invention, the wafers 60 are formed of lead zirconate-titanate crystals, and one electrode 66 is connected to the counterweight 58, and the other electrode 68 is connected to the spacer 62. As a result, the counterweight 58, the upper surface of the top Wafer 60 and the lower surface of the lower wafer 68 are electrically the same point.

The upper horn section 52 functions to provide a firm attachment to the lower crystal 6!). This makes it possible to easily and quickly attach various lower horn sections 54 to the driver 56 without having to bond the lower wafer 60 to a new horn surface each time. The lower horn section 54 is illustrated as having a lower portion 76 which is preferably exponential or tapered in form, namely, has its sectional area varied exponentially, or tapered, along its length, and terminates at its lower end in a rod section of constant diameter.

When high-frequency alternating voltage, for example, a twenty kilocycle alternating voltage is applied to the electrodes 66 and 68, the crystal wafers will contract and expand periodically with the applied voltage and set up mechanical vibrations of constant frequency. This action of the crystals 60 sets up standing vibratory wave forms of constant wave lengths in the transducer and horn assembly 14. It is possible to compute the length of the waves in the Wave forms, which are indicated generally at 72 in FIG. 2. A wave length, A, is determined by the following expression:

where c=velocity of the sound in the material of which the transducer horn assembly 14 is formed f=frequency applied to the driver 56 As a result of the symmetrical arrangement of the wafers 60 with respect to the spacer 62, the spacer electrode 62 must be a point of Zero amplitude, namely, a nodal point. Therefore, knowing that a node is located at the electrode 62 and knowing the wave length a second nodal point in the lower horn section 54 is readily located. At approximately this nodal point, a groove 74 is formed in the lower horn section 54, with the groove 74 being annular in shape and extending about the horn section 54. At a point on the lower horn section 54, adjacent to the groove 74 but spaced therefrom in a direction longitudinally of the horn, namely, in a direction along the horn axis 78, the lower horn section 54 is formed with a downwardly facing shoulder 80.

The top plate 16 has an axial opening 82 formed therein of a size slightly larger than the diameter of the lower horn section 54 at a position between the shoulder 80 and the groove 74. An upwardly facing shoulder 84 is formed on the top plate 16, adjacent to the top surface 86 thereof, so that when the horn section 54 is inserted into the container 18 through the top plate opening 82, the shoulders 80 and 84 are in a facing relation. A sealing ring 88, formed in the preferred embodiment of the invention of a compressible resilient material such as rubber or Teflon, but which can also be formed of metal when desired, is positioned about the lower horn section 54 at a position between the facing shoulders 80 and 84. A restraining member, which in the illustrated embodiment of the invention is a snap ring 90, capable of exerting a tensile force on the lower horn section 54 of a magnitude suflicient to apply the required axial pinch to the sealing ring 88 to achieve a seal, is positioned in the groove 74 and engaged with the bottom surface 92 of the top plate I 16. The groove 74 is located relative to the top plate bottom surface 92 so that when the snap ring 90 is positioned as shown in FIG. 1, the sealing ring 88 is pinched between the shoulders and 84.

The functions of the restraining member which can be assembled in any suitable manner with the lower horn section 54 at approximately a nodal point are the follow- (1) to exert an axial tensile force on the horn section 54 sufficient to compress the sealing ring 88 which provides an effective seal between the horn section 54 and the container top plate 16 without significantly reducing the small-amplitude, high-frequency oscillation of the horn assembly. A conventional seal, as provided by a gasket or O ring arrangement such that a high axial force is necessary to maintain the seal, will substantially reduce or nullify the vibration, whereas an O ring in a conventional cylindrical bore arrangement will not provide an adequate seal except under such conditions that an ambient temperature soft material as rubber can be used. The present arrangement, while suitable for rubber is also applicable with less resilient materials as Teflon, metallic 0 rings, etc., which may be required depending on the nature of the fluid and the temperature; and

(2) to provide a good path for heat conduction from the portion of the horn which is located in the container 18, and thus subject to heating by the fluid 19 in cases in which the fluid 19 is at a high temperature, to the top plate 16 which can be cooled in any suitable manner such as by cooling coils 94, thus draining heat from the horn, and preventing the upper portions thereof from reaching a high temperature.

The construction of the container 18 also contributes to maintaining the upper portions of the born at a low temperature. The top plate 16 and the flange 26 are of sufficiently large cross section, relative to the area for heat conduction provided by the container side walls, to enable the plate 16 and the flange 26 to be maintained at an essentially uniform temperature only slightly in excess of ambient by the cooling coil 94. Thus the sealing members 30 and 88 are also kept at near ambient temperatures. The conical container top wall portion 25 functions to prevent excessive thermal stresses in this region of the container 18 even though there may be a temperature difference on the order of 1500 F. between the top end of the side walls of the container and the flange 26. In other Words, the conical wall section 25 provides a connecting structure between the container 18 and the flange 26 which is inherently more flexible than a cylinder, thus substantially reducing thermal stresses.

It can thus be seen that the sealing means 10 of this invention provides for a cooperative action between a sealing member 88 which is compressible and a restraining member 90 to provide for an axial pinching of the sealing member. This arrangement provides for an effective seal without preventing the desired oscillation. In addition, the extension of the restraining member 90 between the lower horn section 54 and the top plate 16 provides for conduction of heat from the lower horn section 54 to the top plate 16, which is cooled by the coils 94 to maintain the sealing ring 88 in a cooled condition. Furthermore, this arrangement prevents the conduction of excess heat to the driver 56 which must be maintained at a temperature preferably below 200 F., even though the temperature of the liquid 19 may be as high as 2000 F.

The lower horn section 54 is of a length such that the working end or tip thereof is located at an antinode in the wave form 72, namely, a point of maximum amplitude to obtain maximum efficiency from the transducer and the horn assembly 14. In the illustrated embodiment of the invention a test specimen 102 is attached to the tip 109 of the horn section 54 so that the test specimen 102 can be vibrated in the liquid 19 for the purpose of determining the cavitation eifect on the material chosen for thetest specimen. In applications in which some treatment of the fluid 19 is to be accomplished, such as a degassing,

cleaning or homogenizing operation, the test specimen 102 is omitted.

It will be understood that the vibratory unit with sealing device which is herein disclosed and described is presented for purposes of explanation and illustration and is not intended to indicate limits of the invention, the scope of which is defined by the following claims.

What is claimed is:

1. In vibratory horn apparatus which includes a horn member having an axis and a working end, means operatively associated with said horn member for generating standing vibrational waves in said horn of predetermined wave length located such that said working end is disposed at approximately an antinodal point in said waves, a container for fluid having said working end disposed therein, a top on said container having an opening through which said horn member extends, a portion of said horn member disposed at approximately a nodal point in said waves being located in said top opening, said horn member and said top being shaped to form facing shoulders spaced apart in the direction of said axis, a resilient annular sealing ring disposed between said shoulders, and means engaged with and extending between said top and said horn member at a position spaced from said shoulders in a direction axially of said horn member applying a tensile force to said horn member and urging said shoulders toward each other to pinch said sealing ring in the direction of said axis.

2. In combination with a container having a top plate provided with an opening and a vibratable rod extending into said container through said opening; means providing a seal between said rod and said top plate at said opening, said seal comprising an annular sealing ring formed of a resilient material and extended about said rod at a position in which one side of said sealing ring is in engagement with a portion of the top surface of said top plate, means forming a shoulder on said rod engaged with the opposite side of said sealing ring so that when said rod is moved in a direction axially thereof and inwardly of said container said sealing ring is pinched between said shoulder and said top surface portion, said rod having an annular groove therein spaced axially from said shoulder in a direction inwardly of said container, and a snap ring extending into said groove and engaged with said rod at the bottom side of said groove, said snap ring being engaged with the bottom surface of said top plate so as tocontinually apply an axial downward force to said rod of suflicient magnitude to pinch said sealing ring.

3. The combination according to claim 2 further including means connected to said rod for vibrating said rod such that axially spaced portions of said rod are vibrated at diiferent amplitudes varying between zero and a predetermined maximum, said groove being located in a portion of said rod at which the amplitude of vibration is substantially zero.

4. High frequency vibratory apparatus comprising an elongated horn member having a working end and a driven end, means connected to the driven end of said horn member for vibrating said horn member at a predetermined constant frequency to thereby induce vibration in said horn member the amplitude of which varies along the length of said horn between zero and a predetermined maximum, 3. container having liquid therein, said container having the upper end thereof formed with an outwardly flared conical top wall portion terminating in an annular flange, a top cover plate formed with an opening and secured to said flange, resilient sealing means positioned between said top plate and said flange, said horn member extending into said container through said top plate opening to a position in which said Working end thereof is in said liquid, means providing facing shoulders on said horn member and on said top plate at a position surrounding said opening, an annular sealing ring formed of a compressible resilient material disposed between said shoulders, and restraining means engaged with and extending between said horn member and said top plate at a position spaced from said annular sealing ring applying oppositely directed forces to said top plate and said horn member urging said shoulders toward each other so as to compress said annular sealing ring therebetween, said restraining means being located on said horn member substantially at a point of zero amplitude.

5. Apparatus according to claim 4 further including a radiation shield disposed within and mounted on said container at a position between said liquid and said top plate.

References Cited UNITED STATES PATENTS 2,514,080 7/1950 Mason 259--1 2,651,148 9/1953 Carwile 259-1 2,949,900 8/1960 Bodine 31026 2,962,695 11/1960 Harris 2591 2,991,594 7/1961 Brown 5159 3,015,914 1/1962 Roney 5156 3,218,488 11/1965 Jacke 31082 MILTON O. HIRSHFIELD, Primary Examiner. J. D. MILLER, Assistant Examiner. 

1. IN VIBRATORY HORN APPARATUS WHICH INCLUDES A HORN MEMBER HAVING AN AXIS AND A WORKING END, MEANS OPERATIVELY ASSOCIATED WITH SAID HORN MEMBER FOR GENERATING STANDING VIBRATIONAL WAVES IN SAID HORN OF PREDETERMINED WAVE LENGTH LOCATED SUCH THAT SAID WORKING END IS DISPOSED AT APPROXIMATELY AN ANTINODAL POINT IN SAID WAVES, A CONTAINER FOR FLUID HAVING SAID WORKING END DISPOSED THEREIN, A TOP ON SAID CONTAINER HAVING AN OPENING THROUGH WHICH SAID HORN MEMBER EXTENDS, A PORTION OF SAID HORN MEMBER DISPOSED AT APPROXIMATELY A NODAL POINT IN SAID WAVES BEING LOCATED IN SAID TOP OPENING, SAID HORN MEMBER AND SAID TOP BEING SHAPED TO FORM FACING SHOULDERS SPACED APART IN THE DIRECTION OF SAID AXIS, A RESILIENT ANNULAR SEALING RING DISPOSED BETWEEN SAID SHOULDERS, AND MEANS ENGAGED WITH AND EXTENDING BETWEEN SAID TOP AND SAID HORN MEMBER AT A POSITION SPACED FROM SAID SHOULDERS IN A DIRECTION AXIALLY OF SAID HORN MEMBER APPLYING A TENSILE FORCE TO SAID HORN MEMBER AND URGING SAID SHOULDERS TOWARD EACH OTHER TO PINCH SAID SEALING RING IN THE DIRECTION OF SAID AXIS. 